Transitions in refractive index using electro-optic polymers

Abstract

The index of refraction in a length of doped and/or “doped-and-poled” electro-optic polymers is controlled so that a gradual transition from a low Δn to a high Δn, or vice versa, is achieved for use in, for example, a lightguide-to-fiber transition. Multiple methods for creating this gradual transition are disclosed.

1. A method for producing a transition between a first element having a first refractive index difference. (Δn) percentage and a second element having a second Δn percentage higher than the Δn of said first element, comprising the steps of:
 controlling the Δn along a length of electro-optic polymer to achieve a gradual transition from a low Δn to a high Δn along said length; and 
 optically coupling said length of electro-optic polymer between said first element and said second element, 
 wherein said controlling step comprises at least the step of: 
 performing selective deposition on a length of undoped substrate having plural doping regions, using increasing doping levels with each successive doping region. 
 
   
   
     2. The method of  claim 1 , wherein said selective deposition step is performed using a polymer dopant. 
   
   
     3. The method of  claim 2 , wherein said polymer dopant is deposited through photolithographic masking. 
   
   
     4. The method of  claim 3 , wherein said polymer dopant is deposited by spraying said polymer dopant through said photolithographic masking onto said substrate. 
   
   
     5. The method of  claim 3 , wherein said polymer dopant is deposited by dipping said photolithographically-masked substrate into said polymer dopant. 
   
   
     6. The method of  claim 3 , wherein said polymer dopant is deposited using vacuum pyrolisis. 
   
   
     7. A method for producing a transition between a first element having a first refractive index difference Δn percentage and a second element having a second Δn percentage higher than the Δn of said first element, comprising the steps of:
 controlling the Δn along a length of electro-optic polymer to achieve a gradual transition from a low Δn to a high Δn along said length; and 
 optically coupling said length of electro-optic polymer between said first element and said second element, 
 wherein said controlling step comprises at least the step of: 
 performing diffusion doping on a length of undoped substrate having plural doping regions, increasing the diffusion time with each successive doping region. 
 
   
   
     8. The method of  claim 7 , wherein said step of performing diffusion doping comprises the steps of:
 depositing a layer of an impurity source on said entire length of said substrate and leaving said layer on said substrate for a predetermined time period; 
 removing a portion of said layer covering a first of said plural doping regions and leaving the remainder of said layer on said substrate for a second predetermined time period; 
 repeating said removing step for each of said plural doping regions until all of said layer has been removed. 
 
   
   
     9. A transition structure situatable between a first element having a first refractive index difference (Δn) percentage and a second element having a second Δn percentage higher than the Δn of said first element, said transition structure obtainable by the process steps of:
 controlling the Δn along a length of electro-optic polymer to achieve a gradual transition from a low Δn to a high Δn along said length; and 
 optically coupling said length of electro-optic polymer between said first element and said second element, 
 wherein said controlling step comprises at least the step of: 
 performing selective deposition on a length of undoped substrate having plural doping regions, using increasing doping levels with each successive doping region. 
 
   
   
     10. The transition structure of  claim 9 , wherein said selective deposition step is performed using a polymer dopant. 
   
   
     11. The transition structure of  claim 10 , wherein said polymer dopant is deposited through photolithographic masking. 
   
   
     12. The transition structure of  claim 11 , wherein said polymer dopant is deposited by spraying said polymer dopant through said photolithographic masking onto said substrate. 
   
   
     13. The transition structure of  claim 11 , wherein said polymer dopant is deposited by dipping said photolithographically-masked substrate into said polymer dopant. 
   
   
     14. The transition structure of  claim 11 , wherein said polymer dopant is deposited using vacuum pyrolisis. 
   
   
     15. A transition structure situatable between a first element having a first refractive index difference (Δn) percentage and a second element having a second Δn percentage higher than the Δn of said first element, said transition structure obtainable by the process steps of:
 controlling the Δn along a length of electro-optic polymer to achieve a gradual transition from a low Δn to a high Δn along said length; and 
 optically coupling said length of electro-optic polymer between said first element and said second element, 
 wherein said controlling step comprises at least the step of: 
 performing diffusion doping on a length of undoped substrate having plural doping regions, increasing the diffusion time with each successive doping region. 
 
   
   
     16. The transition structure of  claim 15 , wherein said step of performing diffusion doping comprises the steps of:
 depositing a layer of an impurity source on said entire length of said substrate and leaving said layer on said substrate for a predetermined time period; 
 removing a portion of said layer covering a first of said plural doping regions and leaving the remainder of said layer on said substrate for a second predetermined time period; 
 repeating said removing step for each of said plural doping regions until all of said layer has been removed.